2 16 



EEPTILIA 



CLASS III 



have been discovered in the Connecticut Valley, varying between 2*5 cm. and 

 60 cm. in length. Most of these imprints are three-toed, although four- and 

 five-toed tracks also occur, and their paths are often traceable for a number of 

 meters. Since many of these indicated creatures of bipedal gait, early writers 

 (notably Hitchcock in 1837 and 1858) very naturally attributed them to 

 birds, and designated them by various names. The paucity of skeletal remains 

 in the strata where footprints are so conspicuous a feature is remarkable. 



The earliest known Dinosaurs belong to the carnivorous group of Theropoda, 

 and are extremely generalised. Their obvious relations to the Bhynchocephalia, 

 Crocodilia, and Theromorpha have already been discussed, and attention directed 

 to avian resemblances pervading both this and the herbivorous sub-orders. It 

 need only be repeated in this connection that, in spite of the remarkable simi- 

 larity between birds and Dinosaurs, there is no evidence to prove that the 

 former have come down to us through any known type of the latter. And 

 yet it would appear rather more probable that the avian phylum should have 

 originated from primitive Dinosaurs — that is to say, from a Dinosaur-avian 

 stem, than that the two groups arose independently from some common stock. 



TABLE SHOWING VERTICAL RANGE OF THE DINOSAURIA. 



[The text for the introductory portion of the preceding chapter on Dinosaurs 1ms been 

 to a slight extent by Professor H. F. Osborn ; that for the systematic part has been 

 revised by Mr. J. B. Hatcher, of the Carnegie Museum at Pittsburgh. -Editor:] 



Order 9. PTBROSAURIA. Kaup. (Omithosauria, Fitzinger.) * 



Reptiles of more or less bird-like aspect, with hollow bones, well-formed articula- 

 tions, a„d fore-limbs adapted for flight. Skull with acuminate snout, and long 

 1 Literature : 



BalW^Tn /V~ itiS f' e Bek ' uc,,tun S < Ier Pterodactylus-Arten (Sitzungsber. naturf. Gesellseh. 

 1878 ' !/, ■/ AiTSr™ 8 ' a \ Ueber Pterodactylus suevicus (Palaeontogr. vol. XXV. p. 163). 

 Ooldfuss, A.. Reptihen aus dem lithographischen Schiefer (Nova Acta Acad. Leop. vol. XV 



